Create redux.md

docs/redux.md

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+# Usage with Redux
+
+Although RNFirebase usage requires a React Native environment, it isn't tightly coupled which allows for full flexibility
+when it comes to integrating with other modules such a [`react-redux`](https://github.com/reactjs/react-redux). If you wish to use
+a Redux library designed for Firebase, we suggest taking a look at [`react-redux-firebase`](http://docs.react-redux-firebase.com/history/v2.0.0/docs/recipes/react-native.html)
+for implementation with this module.
+
+## Standalone integration
+
+Although the following example works for a basic redux setup, it may differ when integrating with other redux middleware.
+Imagine a simple TODO app, with redux we're able to abstract the Firebase logic out of components which allows for greater
+testability and maintainability.
+
+?> We use [`redux-thunk`](https://github.com/gaearon/redux-thunk) to provide async actions.
+
+### Action Creators
+
+```js
+// Actions
+export const subscribe = () => {
+  return (dispatch) => {
+    firebase.database().ref('todos').on('value', (snapshot) => {
+      const todos = [];
+      
+      snapshot.forEach((childSnapshot) => {
+        todos.push({
+          id: childSnapshot.key,
+          ...(childSnapshot.val()),
+        })
+      })
+      
+      dispatch({
+        type: 'TODO_UPDATE',
+        todos,
+      })
+    })
+  }
+}
+
+// Methods
+export const addTodo = text => {
+  firebase.database().ref('todos').push({
+    text,
+    visible: true,
+  })
+}
+
+export const completeTodo = id => {
+  firebase.database().ref(`todos/${id}`).update({
+    visible: false,
+  })
+}
+
+```
+
+Instead of creating multiple actions which the reducers handle, we instead subscribe to the database ref and on any changes,
+send a single action for the reducers to handle with the data which is constantly updating.
+
+### Reducers
+
+Our reducer now becomes really simple, as we're able to simply update the reducers state with whatever data has been returned
+from our Firebase subscription.
+
+```js
+const todos = (state = {}, action) => {
+  switch (action.type) {
+    case 'TODO_UPDATE':
+      return { ...action.todos };
+  }
+  
+  return state;
+}
+
+export default todos;
+```
+
+### Component
+
+We can now easily subscribe to the todos in redux state and get live updates when Firebase updates.
+
+```js
+import React from 'react';
+import { FlatList } from 'react-native';
+import { connect } from 'react-redux';
+import { subscribe, addTodo, completeTodo } from '../actions/TodoActions.js';
+...
+
+class Todos extends React.Component {
+
+  componentDidMount() {
+    this.props.dispatch(
+      subscribe()
+    );
+  }
+  
+  onComplete = (id) => {
+    this.props.dispatch(
+      completeTodo(id)
+    );
+  };
+  
+  onAdd = (text) => {
+    this.props.dispatch(
+      addTodo(text)
+    );
+  };
+  
+  render() {    
+    return (
+      <FlatList
+        data={this.props.todos}
+        ...
+      />
+    );
+  }
+}
+
+function mapStateToProps(state) {
+  return {
+    todos: state.todos,
+  };
+}
+
+export default connect(mapStateToProps)(Todos);
+```